Technology in Stellaris is divided into 3 research areas with each area corresponding with one of the research resources: Engineering, Physics and Society. Additionally, each of the ~300 techs belongs to one of 12 subcategories divided between the areas (most appearing pre-dominantly in one area though not exclusively).

The user interaction aspect utilizes a card shuffle approach rather than a traditional tech tree presentation, thereby introducing an element of semi-randomness into the system.

Contents

Technology interface. Every slot here can have one research project active at a time and every research area has its own slot.

There are three different main research areas in-game, with each area corresponding with one of the research resources. Additionally, each research area has multiple subcategories, for a total of 12 such subcategories, and every tech belongs to one of these subcategories.

The "card" system. Every time a research project is to be initiated, the game will draw a hand of cards like this one from which the player then can pick one technology to research.

Although the underlying technology system is based on the familiar tech tree structure, it does away with its standard interaction/presentation in favor of the card shuffle approach. This injects a semi-random element into research, making it somewhat less predictable as well as more non-linear.

Whenever the player is prompted to initiate a research project, the game gives them a "hand of cards" consisting of a semi-random selection of technologies available for research which are picked randomly from a hidden "deck of cards" consisting of all valid research options that can appear.

Every time the player meets the requirements for a given technology to become obtainable, the technology in question is added into the main "card deck" and will then have a chance of appearing in the "card hand" whenever the game draws a new hand for the player to pick from. There are two basic parameters affecting a tech's chances of appearing in a given card hand:

Tiers – Technologies are divided into 6 levels (T0 to T5) of advancement. Higher tier technologies require obtaining a certain number of technologies from the preceding tier in the same area of research (set at 6 for all tiers[1]) before they become available as research alternatives.

Weight – A base value denoting the relative chance (out of all the valid options) of a particular technology to be drawn as an alternative. This may be further modified by an empire's composition (ethics, civics, etc.) and its current state (scientist's traits, past tech, etc.).

To further increase variation, a tech which appeared as an alternative in the previous card hand will have its weight set to 0 in the next prompt.

As a general rule of thumb, the more advanced a technology is, the lower its weight (and the higher its cost). Systematically important techs (e.g. terraforming) have a higher weight (typically between 150% and double normal) to help ensure empires get a chance to research them, whereas rare technologies have significantly lower weight (typically one-eighth normal without the matching expertise). Some factors increase the weight of rare techs:

Being in a level 3 or higher Research Cooperative federation with another member who knows the tech doubles the weight.

The Technological Ascendancy ascension perk increases the weight by 50%.

Let's assume the game draws a card hand of 3 techs: Armored Torpedoes, Autocannons, and Exotic Gas Refining. Additionally, the lead engineering scientist has a Propulsion field expertise (matching Armored Torpedoes) and the previous card hand had Autocannons as an available option.

If these were the only three valid techs and only one tech were to be drawn, then each tech's chances of being drawn would be 29.1%, 12.5%, and 56.4% respectively (rounded to 1 decimal place). Realistically there are usually many more valid picks and so the probability of picking any given tech is significantly lower than the figures given here.

Additionally, some research cards may be gained as permanent alternatives. They appear below the regular alternatives and are distinguished from them by a golden border surrounding the tech card's bezel. These alternatives are usually acquired (along with some partial progress) through post-battle debris analysis, from special projects or event chains. These options will always appear as available options when drawing a new card hand and will remain as such until completed.

If need be, it is possible to change an on-going research project at any point - without incurring penalties - in order to continue researching it at a later time. It is important to note, however, that the saved progress does not scale with changes occurring to technology costs (for better or for worse). This tends to lead to the tech's completion percentage getting lower as the empire continues to further exceed its administrative capacity.

As opposed to a permanent alternative, there is no guarantee that the technology in question will appear in the next card hand drawn.

Research output which is not being used for research at the time is being accumulated as stored research. Alternatively, it may also include research resources gained from other avenues such as debris analysis, anomalies, events, and etc.

This method allows for a more "relaxed" research by eliminating the loss of research points due to forgetting to pick a research project while, at the same time, also simulating accelerated periods of research (as opposed to sudden "jumps") caused by newfound knowledge sources. The current storage levels can be seen by hovering over the appropriate resources.

The expenditure rate of stored research can be expressed as follows:

Example

An empire produces +24 Engineering research a month and has just finished debris analysis granting it +1000 Engineering research (stored research).

The empire will supplement its Engineering research by an additional +24 research points for the first 41 months and by another +16 research points in the following month, after which the Engineering stored research bank will completely deplete.

Research speed represents a given expertise in a particular research area or field leading to shortened research time of related technologies.

Research speed boosts the perceived research production in the following manner:

The most immediate sources of research speed modifiers are the 3 lead scientists. As the applied bonus depends on a scientist's skill level and overall traits, it is recommended to assign newly recruited scientists to command a science ship. Scientists on exploration duty tend to gain experience faster and, if one is in luck, they may also gain a new trait beneficial to research while leveling up.

Example

An empire is a Materialist and produces +24 Engineering research a month. It has a lead engineering scientist with a Propulsion field expertise while researching Armored Torpedoes.

Note: A research area without an acting lead scientist receives a penalty to research speed.

As a game progresses, research option choices will begin to include progressively more advanced and correspondingly more expensive technologies.

Each technology has a base cost that applies as long as an empire does not exceed its Administrative Capacity. Once that happens, the research cost will be increased by 0.4% for each point of exceeded Administrative Capacity. This can be fixed by employing more bureaucrats.

Research progress is one of the key elements affecting the time it takes to discover new technologies. It is formulated as follows:

While it is possible for the monthly research progress to remain constant during the course of researching a certain technology, it is more than likely to fluctuate - for better or for worse - due to consequences of various actions (such as exploration, empire development, expansion, etc.). This, in turn, may increase or decrease the total research time of a given tech.

Example

The empire from the previous examples (same setup) has just finished debris analysis granting it +10% research progress in Armored Torpedoes along with +1000 Engineering research (stored research).

This setup will generate the following monthly research progress:

Assuming no further changes will impact the above setup, the total research time of the tech would be:

Note:Partial research can refer to debris analysis, previous research, event rewards and etc.